Hybrid tile metal matrix composite armor
A lightweight armor system may comprise multiple reinforcement materials layered within a single metal matrix casting. These reinforcement materials may comprise ceramics, metals, or other composites with microstructures that may be porous, dense, fibrous or particulate. Various geometries of flat plates, and combinations of reinforcement materials may be utilized. These reinforcement materials are infiltrated with liquid metal, the liquid metal solidifies within the material layers of open porosity forming a dense hermetic metal matrix composite armor in the desired product shape geometry. The metal infiltration process allows for metal to penetrate throughout the overall structure extending from one layer to the next, thereby binding the layers together and integrating the structure.
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This application claims the benefit of U.S. Provisional Application No. 61/005,127 filed 3 Dec. 2007.
FIELD OF THE INVENTIONThis invention relates to lightweight armor systems in general and more specifically to an integrated, hybrid ceramic tile panel system comprising dense ceramic plate layers combined with metal and/or metal matrix composite (MMC) enveloping structures which include metal rich posts for energy absorption and for attachment of the composite structure to a backing plate.
BACKGROUND OF THE INVENTIONMany different kinds of lightweight armor systems are known and are currently being used in a wide range of applications, including, for example, aircraft, light armored vehicles, and body armor systems, wherein it is desirable to provide protection against bullets and other projectiles. While early armor systems tended to rely on a single layer of a hard and brittle material, such as a ceramic material, it was soon realized that the effectiveness of the armor system could be improved considerably if the ceramic material were affixed to or “backed up” with an energy absorbing material, such as high strength Kevlar fibers. The presence of an energy absorbing backup layer functions to catch the fragments of an incoming projectile but without significantly reducing the spallation of the ceramic caused by impact of the projectile.
Testing has demonstrated that such multi-layer armor systems tend to stop projectiles at higher velocities than do the ceramic materials when utilized without the backup layer. While such multi-layer armoring systems are being used with some degree of success, they are not without their problems. For example, difficulties are often encountered in creating a multi-hit capability armor with multi-layered material structure having both sufficient mechanical strength and ballistic shock resistance as well as sufficient bond strength at the layer interfaces.
Partly in an effort to solve the foregoing problems, armor systems have been developed in which a “graded” ceramic material having a gradually increasing dynamic tensile strength and energy absorbing capacity is sandwiched between the impact layer and the backup layer. An example of such an armor system is disclosed in U.S. Pat. No. 3,633,520 issued to Stiglich and entitled “Gradient Armor System”.
The armor system disclosed in the foregoing patent comprises a ceramic impact layer that is backed by an energy absorbing ceramic matrix having a gradient of fine metallic particles dispersed therein in an amount from about 0% commencing at the front or impact surface of the armor system to about 0.5 to 50% by volume at the backup material.
While the foregoing type of armor system was promising in terms of performance, it has been discovered by the present inventors that a dense ceramic armored tile system intimately encapsulated in solid metal and/or metal matrix composites and including cast-in energy absorbing post structures reduces “spallation” caused by projectile impact and has not yet been presented in the art.
SUMMARY OF THE INVENTIONThe armor tile system according to the present invention comprises one or more dense ceramic plates encapsulated in solid metal and/or metal matrix composites (MMC) and includes cast-in integrated energy absorbing post structures extending outward from the tile(s). The enveloping aluminum or MMC may contain “reinforcing bars” of strong metal alloy wires to create a re-bar reinforced ductile aluminum or MMC skin, or various configurations of rods or metal sheets, which acts to dissipate energy upon projectile impact while maintaining the structural integrity surrounding the impact zone.
Each individual hybrid tile may comprise a structure of dense ceramic plate(s) and the hybrid tile can be bonded to an aluminum backing plate via extending post structures by methods known in the art such as welding, adhesive bonding, or mechanical swaging. Various arrays of dense ceramic plates, including a single dense plate or a plurality of dense plates may be utilized (1×1, 2×2, 4×4, 2×8, etc) within a hybrid tile and multiple tiles may be mounted to a backing plate depending on the area to be protected.
The armor tile system of the present invention is created utilizing a molten metal infiltration process. First, a mold cavity comprising elongated holes machined into its base is provided. Next, one or more dense ceramic plates are placed within the mold cavity resting on one or more spacers that separate the bottom surface of the ceramic plates(s) from the base of the mold cavity to create a space therebetween. The spacers may be a dense or porous ceramic, or metal or combinations thereof.
The dense ceramic plates are further positioned within the mold cavity to create a controlled space between adjacent plates via alignment spacers positioned between adjacent plates to keep the plates from shifting during metal infiltration. The alignment spacers can be a soft metal or hard ceramic, porous or dense material. The dense ceramic plates and spacers include ceramics which may include open porosity only at the material surface and that are devoid of open interconnected porosity within the interior of the materials.
A mold typically contains one or more ceramic plates however various geometries of flat plates, and combinations of dense layers may be utilized. The mold may further contain metal “rebar” wire or various configurations of rods or metal sheets, placed around the edges of the mold cavity, over the surface of the ceramic plates, and between the plates, to create a reinforced ductile aluminum or MMC skin.
A second set of spacers are next placed on the ceramic plates top surface to create a space between the mold cavity cover and the ceramic plates top surface. A plurality of ceramic plates and spacers may also be stacked according to the shape of the mold cavity and desired ballistic resistance. The mold cavity is next infiltrated under pressure with molten metal allowing for metal to penetrate into any open porosity of the dense ceramic plate layer surfaces and spacer open porosity and through or around areas within the mold cavity that contain open spaces, thereby binding the layers together, and encapsulating the dense ceramic plates and spacers into an integrated tile panel.
The elongated holes in the mold cavity base are also filled with liquid metal that once solidified then form integrated cast-in post structures. These posts may be metal rich or contain other dense or porous ceramic or metal inserts and are provided for energy absorption and attachment of the composite tile structure to a backing plate.
The mold chamber is fabricated to create the final shape or closely approximate that desired of the final product. The hybrid armor tile is next demolded and comprises a hybrid structure of metal matrix composite and ceramic plates with an encapsulating aluminum rich skin and/or metal matrix composite (MMC) enveloping structure. Integrated cast in metal rich post structures are provided for both 1.) energy absorption and 2.) attachment of the composite tile structure to a backing plate. The length, diameter, draft angle and spacing of the posts are variable to meet a desired ballistic threat and blast over-pressure.
A fraction of the posts may be used to attach the composite tile structure to the backing plate, and may be recessed within the backing plate or affixed to the surface of the backing plate. The other fraction of posts being shorter and with post ends either contacting the backing plate, or raised above the backing plate. The attachment posts have a length to allow a separation between the backing plate and the hybrid tile body. The posts help absorb shock and the space between the hybrid tile and backing plate help to deflect an overpressure blast wave.
Additionally, a rubber or adhesive material may be present between the post ends and backing plate and as a filler placed between adjacent posts to further enhance ballistic or blast energy absorption by attenuating shock waves after projectile impact or blast over-pressure.
The dense layers can include an infinite combination of dense material types and geometries. These dense layers may comprise inorganic material systems such as ceramics, metals, carbon/graphite materials, or composites with dense microstructures. Other dense layers include ceramic structures containing interior voids or hollow regions (which are not connected to the surface). The geometries can be in the form of flat plates of varying thickness, compound curved shapes, spheres, cylinders, and of multiple sequences and combinations of the dense materials.
The dense layers are wetted with liquid metal which chemically bonds and/or mechanically infiltrates any open surface porosity and then solidifies and binds the layers together to create a coherent integral structure. The dense layers can be selected according to their denseness and fraction of void volume at the material surface that are to be infiltrated with liquid metal. The selection of different dense material types allows the designer to vary thermal expansion coefficients throughout the structure to create varying stress states for increased effectiveness of the armor tile system. The selection of different material types may also be based on hardness, strength, toughness, and weight attributes of the individual material types desirable for projectile impact protection.
The invention is best understood from the following detailed description when read in connection with the accompanying drawings, which illustrate an embodiment of the present invention:
FIG. 6A1 illustrates a sectional view of an alternative embodiment of spacer 20 and post 6B of tile panel 60 after metal infiltration.
A hybrid tile armor system 10 of the present invention is illustrated in
The dimensions of the mold cavity may be flat or include compound curves required for applications such as personal body armor. Mold cavity 15 includes a plurality of openings 15A milled into mold 15 bottom surface 15B which are subsequently filled with molten metal during the infiltration casting process to form posts 6A and 6B (see
Referring to
The density of openings 15A could range from about 2% to about 40% of the surface area of bottom surface 15B. It is understood that various arrays of dense ceramic tiles or plates, including a single dense plate or plurality of plates (1×1, 2×2, 4×4, 2×8, etc) may be utilized to form a hybrid tile panel and multiple panels may be mounted to a backing plate to form a larger armor panel structure (see
Referring to
The spacers 20 also serve as a reinforcement point to enhance stiffness of the hybrid tile armor tile panel 60 system and may also act to anchor posts 6A and 6B as illustrated in FIGS. 6A and 6A1. Spacers 20 may also include a through hole 6B1 in selected spacer 20 locations covering openings 15A (See
These reinforced posts can be selected for either posts 6A or 6B according to ballistic threat requirements. Referring to
The thickness of dense ceramic plates 25 can range from about 0.020 inches to about 2 inches or more. The plates 25 are set in the mold cavity such that space 25A between adjacent ceramic plates is between about 0.01 to about 0.5 inches and the space between the ceramic plate outer periphery 25B and the mold cavity internal side surface 25C is approximately ½ of the space 25A. The controlled spaces 25A defined above and the space between the tile outer periphery 25B and the mold cavity internal side surface 25C is maintained via alignment spacers positioned between adjacent ceramic plates 25 to keep the plates 25 from shifting during metal infiltration. The alignment spacers can be a soft metal or hard ceramic, porous or dense material.
Referring to
Other possibilities contemplated for the “rebar” reinforcement may include various configurations of rods, woven fibers or wires, or metal sheets, placed around the edges of the mold cavity, over the surface of the ceramic tiles, and between the tiles, to create a reinforced ductile aluminum or stiff Metal Matrix Composite (MMC) skin. Next, a second set of one or more spacers 20A are placed upon the top surface of tiles 25, the spacers 20A, which may be of different composition and size than spacers 20, and may be placed directly above and parallel to spacers 20 to aid in the reinforcement, toughness and stiffness of the hybrid tile armor system 60.
The inventors have found that the alignment of the porous ceramic spacers 20 and 20A can facilitate abrasive type through hole machining. As illustrated in
The number of layers is determined by the mold size and desired ballistic resistance. A cross-section of the stacked layers of dense ceramic plates 25 and stacked layers of spacers 20 and 20A of an embodiment incorporating the principles of subject invention is illustrated in a sealed mold cavity 15 without re-bar reinforcement (
Dense ceramic plates 25 comprise a microstructure designed without interconnected porosity and having a predetermined fraction of void volume or open structure at its surface, or zero void volume or open structure at its surface. If a void volume is present it is filled and bonded with molten metal subsequent to metal infiltration casting. Dense ceramic plates 25 may be dense ceramic such as aluminum oxide, silicon carbide, boron carbide, silicon nitride, chemical vapor deposit diamond or composites of ceramics. Dense ceramic plates 25 may be a dense metal such as titanium, tungsten, molybdenum, and depleted uranium or alloys.
Other suitable dense materials include but are not limited to glass-ceramics, and other inorganic material systems which are compatible with molten metal processing and which can contribute to ballistic resistance of the integrated system. Dense materials such as high strength steels, metal alloys, and ceramic alloys may be used in subject invention. Dense ceramic plates 25 include between 0 and 20% surface porosity with the interior of the dense materials not susceptible to metal infiltration.
The dense materials may include “voids” or open spaces within their interior, however, no interconnected porosity is present which would provide a path for metal infiltration from the surface to the interior of dense materials. Spacers 20 and 20A may be ceramic or metal and in the form of particulates or fiber. Spacers 20 and 20A may also be in the form of metal sheets, rods, wires and weaves functioning to separate the ceramic tile layers. The ceramic and/or metal particulate or fiber reinforcements within the metal matrix include materials such as aluminum oxide, carbon, graphite, silicon carbide, boron carbide, titanium, tungsten, nickel, molybdenum, copper, aluminum and other anticipated ceramics or metal materials.
Spacers 20 and 20A having an interior open porosity would range between about 30% and about 90% prior to metal infiltration. Referring to
The Al infiltration process causes aluminum to penetrate throughout the overall structure and into any surface open porosity of dense ceramic plates 25. Spacers 20 and 20A may have a predetermined fraction of void volume or open structure throughout the material structure that becomes filled with molten metal or become bonded metallurgically or mechanically to ceramic plates 25 subsequent to metal infiltration casting.
The Al infiltrant solidifies within and around the material layers extending from one layer interface to the next, thus binding the layers together and integrating the structure. While molten aluminum is the embodiment illustrated other suitable metal infiltrants include but are not limited to aluminum alloys, copper, titanium and magnesium, and other metal alloys cast from the molten liquid phase. The liquid metal infiltration process is described in U.S. Pat. No. 3,547,180 and incorporated herein by reference for all that it discloses.
Referring to
Any open surface voids within the dense ceramic plates 25, if present, and open porosity within spacers 20 and 20A are filled with aluminum during the Al infiltration process including space 25A between ceramic plates 25. As illustrated in
Referring to
As illustrated in
A space 30A may be created below post 6B depending on the depth of the bore into backing plate 7 and extent to which post 6B is inserted into the bore. The backing plate 7 serves as a mounting platform to attach the armor panel to the object requiring protection. The backing plate 7, in combination with armor tile 60, may be made of aluminum, steel, titanium, fiber reinforced epoxy, or other metal or composite structures. As illustrated in
A single backing plate 7 may be drilled itself for attachment of the panel 60 and aligned spacers 20 and 20A may also serve as a drillable medium attachment point.
Claims
1. A hybrid tile metal matrix composite armor, comprising:
- at least one hard layer, each of said at least one hard layer comprising a plurality of dense ceramic plates, said plurality of dense ceramic plates further comprising a spacing therebetween,
- a containment layer encasing said at least one hard layer, said containment layer formed around said plurality of dense ceramic plates, said containment layer including a plurality of post structures extending outward therefrom, said plurality of post structures including a fixed length plurality of first posts and a fixed length plurality of second posts, and
- a backing plate, said backing plate including top surface mounting recesses, said mounting recesses engaging said fixed length plurality of second posts up to a point when said fixed length plurality of first posts ends are flush with said backing plate top surface.
2. A hybrid tile metal matrix composite armor as in claim 1, further including:
- at least one spacer layer, said at least one spacer layer comprising at least one spacer, said at least one spacer having a fraction of void volume,
- said at least one spacer further comprising a metal, said metal infiltrated within said void volumes of said at least one spacer, said containment layer encasing said at least one hard layer and said at least one spacer layer, said containment layer formed around said plurality of dense ceramic plates and said at least one spacer, said containment layer including a plurality of integrated post structures extending outward therefrom.
3. A hybrid tile metal matrix composite armor as in claim 2 wherein said at least one spacer layer is positioned as the top layer and the bottom layer of said metal matrix composite armor.
4. A hybrid tile metal matrix composite armor as in claim 1, wherein said plurality of post structures have variable diameters, lengths, and spacings therebetween.
5. A hybrid tile metal matrix composite armor as in claim 1, wherein a space exists between said plurality of short fixed length posts ends and said backing plate top surface.
6. A hybrid tile metal matrix composite armor as in claim 5, wherein said space is filled with rubber.
7. A hybrid tile metal matrix composite armor as in claim 1, wherein the space between said plurality of post structures extending outward from said containment layer are filled with rubber.
8. A hybrid tile metal matrix composite armor as in claim 1, wherein said plurality of post structures have a surface area density from about 2% to about 40% of the surface area of said hybrid tile metal matrix composite armor.
9. A hybrid tile metal matrix composite armor as in claim 1, wherein said spacing between said plurality of dense ceramic plates tiles is from about 0.01 inches to about 0.5 inches.
10. A hybrid tile metal matrix composite armor as in claim 3, wherein the containment layer thickness around the sides of said at least one hard layer is one half of said spacing between said plurality of dense ceramic plates.
11. A hybrid tile metal matrix composite armor as in claim 2, wherein at least one spacer of said at least one spacer layer has a surface area up to and including the surface area of one of said at least one hard layer.
12. A hybrid tile metal matrix composite armor as in claim 2, wherein said at least one spacer are from about 0.005 to about 0.5 inches thick.
13. A hybrid tile metal matrix composite armor as in claim 3, wherein at least one of said at least one spacers of said bottom layer includes a through hole, said through hole infiltrated with metal and integral with said post structures extending outward from said containment layer.
14. A hybrid tile metal matrix composite armor as in claim 2, wherein reinforcement material selected from the group consisting of wire, rods, and metal sheets may be substituted for at least one spacer of said at least one spacer layer.
15. A hybrid tile metal matrix composite armor as in claim 10, wherein reinforcement material selected from the group consisting of wire, rods, and metal sheets may be placed around said sides of said at least one hard layer, over the surface of said at least one hard layer, and between said plurality of dense ceramic plates.
16. A hybrid tile metal matrix composite armor as in claim 15, wherein said wire material has a thickness of from about 0.0005 inches to about 0.5 inches.
17. A hybrid tile metal matrix composite armor as in claim 1, wherein each of said plurality of dense ceramic plates is from about 1 inch by 1 inch in dimension to about 16 inch by 16 inch in dimension.
18. A hybrid tile metal matrix composite armor as in claim 1, wherein each of said plurality of dense ceramic plates have a thickness from about 0.02 inches to about 2 inches.
19. A hybrid tile metal matrix composite armor as in claim 1, wherein said plurality of long fixed length posts are welded into said mounting recesses.
20. A hybrid tile metal matrix composite armor as in claim 1, wherein the space between said plurality of short and long fixed posts is filled with rubber or a similar material.
21. A hybrid tile metal matrix composite armor as in claim 1, wherein a plurality of said metal matrix composite armor is mounted adjacent to each other.
22. A hybrid tile metal matrix composite armor as in claim 21, wherein said adjacently mounted plurality of said metal matrix composite armor are spaced 0 to 0.01 inches apart for optimum ballistic deterrence.
23. A hybrid tile metal matrix composite armor as in claim 2, wherein said at least one spacer layer fraction of void volume prior to metal infiltration is between about 30% and about 80%.
24. A hybrid tile metal matrix composite armor as in claim 2, wherein said at least one spacer layer comprises a reinforcement material selected from the group consisting of ceramic, glass, or glass-ceramic, including oxides and non-oxide ceramics, graphite and carbon formed materials.
25. A hybrid tile metal matrix composite armor as in claim 1, wherein at least one of said at least one hard layer comprises a ceramic material selected from the group consisting of aluminum oxide, silicon carbide, boron carbide, silicon nitride and chemical vapor deposit diamond.
26. An integrated layered armor as in claim 1, wherein at least one of said at least one hard layer comprises a metal material selected from the group consisting of titanium, tungsten, molybdenum, and depleted uranium.
27. A hybrid tile metal matrix composite armor as in claim 1 wherein said backing plate is substantially parallel to said containment layer.
28. A hybrid tile metal matrix composite armor as in claim 1, wherein said spacing between said plurality of dense ceramic plates and said containment layer further comprise a metal therein.
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- PCT/DE07/01921.
Type: Grant
Filed: Jul 22, 2008
Date of Patent: Mar 13, 2012
Assignee: CPS Technologies (Norton, MA)
Inventor: Richard Adams (Bolton, MA)
Primary Examiner: Bret Hayes
Assistant Examiner: Reginald Tillman, Jr.
Application Number: 12/220,147
International Classification: F41H 5/02 (20060101);